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Regulation of the hetero-octameric ATP phosphoribosyl transferase complex from Thermotoga maritima by a tRNA synthetase-like subunit (2005)

Vega, M. Cristina ; Zou, Peijian ; Fernandez, Francisco J. ; [et al.]

Oxford, UK : Blackwell Science Ltd

Molecular microbiology 55 (2005), S. 0

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ISSN: 1365-2958

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology , Medicine

Notes: The molecular structure of the ATP phosphoribosyl transferase from the hyperthermophile Thermotoga maritima is composed of a 220 kDa hetero-octameric complex comprising four catalytic subunits (HisGS) and four regulatory subunits (HisZ). Steady-state kinetics indicate that only the complete octameric complex is active and non-competitively inhibited by the pathway product histidine. The rationale for these findings is provided by the crystal structure revealing a total of eight histidine binding sites that are located within each of the four HisGS–HisZ subunit interfaces formed by the ATP phosphoribosyl transferase complex. While the structure of the catalytic HisGS subunit is related to the catalytic domain of another family of (HisGL)2 ATP phosphoribosyl transferases that is functional in the absence of additional regulatory subunits, the structure of the regulatory HisZ subunit is distantly related to class II aminoacyl-tRNA synthetases. However, neither the mode of the oligomeric subunit arrangement nor the type of histidine binding pockets is found in these structural relatives. Common ancestry of the regulatory HisZ subunit and class II aminoacyl-tRNA synthetase may reflect the balanced need of regulated amounts of a cognate amino acid (histidine) in the translation apparatus, ultimately linking amino acid biosynthesis and protein biosynthesis in terms of function, structure and evolution.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2958.2004.04422.x

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Towards the Understanding of the Folding of Methylene Units in the Glutamine Residue (1996)

Alemán, Carlos ; Vega, M. Cristina ; Navarro, Eloísa ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Peptide Science 2 (1996), S. 364-370

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ISSN: 1075-2617

Keywords: conformation ; glutamine ; folding ; simulation ; Chemistry ; Biochemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The conformational preferences of the methylenic sequence in the side chain of the glutamine residue were investigated by ab initio and semi-empirical quantum mechanical calculations and examination of both the Brookhaven Protein Databank and Cambridge Structural Data Base. The results were analysed on the basis of our previous findings about the folding of methylene groups in aliphatic segments. Both energy calculations and the crystallographic structure of small peptides indicate that methylene units of the glutamine residue tend to fold in a gauche conformation. In contrast, such groups usually adopt an all-trans conformation in proteins due basically to the entropic and solvent contributions. These results have been demonstrated by computing the entropic correction to the free energy and evaluating the solvent effects through SCRF calculations

Additional Material: 3 Ill.